The present invention relates to character recognition systems and, more particularly, to memory units for use in character recognition.
In character recognition systems the document to be read is located in a reading station by means of a document transport. At the reading station the difference in reflectance between a character and the document background is detected optically and is converted into an electrical signal that is stored in a memory. This conversion can be done a line at a time and the data can be stored in a line memory. Once in the line memory the data can be searched to locate the character perimeter and can be processed (e.g. thinned and scaled) as shown in U.S. Pat. No. 3,541,511 to Genchi et al. Then the data is transferred to a classifier memory where the character is identified, e.g., by comparing the data to character masks such as is explained in U.S. Pat. No. 3,766,520 of Patterson.
The typical line memory stores lines of data (e.g. words) which can be read out in line or word form under the control of the system controller. While this is a convenient way to store data, it is an inefficient form for the data when its perimeter is sought. The top, bottom, left and right edges of the character can be located more easily if two-dimensional arrays of rows and columns of the memory are supplied to a position detector or perimeter detector circuit. Also, the area of the character is more easily determined with such an array of data.
With most character recognition systems information from the line memory is obtained by the controller and is fed to a position detector or perimeter trace circuit where it is determined if the data contains part of the transition from the background to the character or vise versa. The position detector itself may be under program control either from the controller or its own computer. Such a procedure is slow and inefficient, since the steps of reading and executing instructions must be carried out with the system controller. Therefore, a faster and more efficient machine could be realized if the line memory was capable of supplying 4.times.4 arrays of data to the position detector independent of the system controller on its bus.